The present invention generally relates to an optical printer for example, a fixed, a portable printer and the like, for optical writing on a recording medium; and more particularly to an optical printer and a print head therefor, wherein a plurality of filters are selectively alternated or changed with respect to a common luminous source.
As is well known, a print head in a typical optical printer includes a luminous source in which a plurality of fine luminous dots are juxtaposed along a line, the luminous source moving from a main scanning direction juxtaposing to the luminous dots to a sub-scanning direction perpendicular to the main scanning direction so as to irradiate dot-type lights on a recording medium, forming a desired image thereon. A variety of luminous elements such as a fluorescent luminous tube or LED and the like are utilized as the luminous source.
There is schematically shown in FIG. 14 a structure of a print head incorporated in a conventional optical printer, for example, a portable color printer and the like and there is shown in FIG. 15 a partial structure of the print head, with some parts omitted therefrom.
As shown in FIG. 14, a print head 100 is made to reciprocate in a sub-scanning direction, e.g., with respect to a film 102 acting as a recording medium placed at a predetermined position. That is, as shown in FIG. 15, the print head 100 is guided by a pair of guide shafts 104 which are positioned parallel to the sub-scanning direction and is connected to a pulse motor 106 through a wire 108 to be driven, thereby allowing the print head 100 to reciprocate in the sub-scanning direction. Further, the print head 100 includes a luminous element 110 acting as a luminous source, the luminous element 110 having a plurality of luminous dots that are positioned parallel to the main scanning direction. Light emitted from the luminous element 110 passes through three filters R,G,B as described hereinafter and is imaged through a reflective optical element(mirror) 112, a single optical system(lens) 114, and a reflective optical element (mirror) 116 to the film 102.
As shown in FIG. 14, each of the red filter R, the green filter G and the blue filter B is disposed on an irradiating side of the luminous element 110 to be alternated or changed as desired. As shown in FIG. 15, the three filters R,G,B are mounted on a common filter holder 118 in such a way that longer sides thereof are parallel to the main scanning direction and shorter sides are parallel to the sub-scanning direction. The filter holder 118 is provided with a projection 120 for manipulating the filter holder 118, the projection 120 projecting in the sub-scanning direction. Also, the projection 120 is maintained between a guide bearing 122 and a position determining bearing 124. The position determining bearing 124 is biased by a spring 126 and engaged with any one of three cut-off portions 128 formed on the projection 120. The filter holder 118 is compressed by a spring 130 toward a predetermined direction in the sub-scanning direction. An abutment 132 is disposed at a predetermined distance from the projection 120 and a reset plate 134 is disposed at an opposite side therefrom in such a manner that the print head 100 is sandwiched therebetween. That is, when the projection 120 of the filter holder 118 comes in contact with the abutment 132 as a result of the print head 100 moving, the filter holder 118 also moves, allowing the filters R,G,B to be alternated or changed as desired. Further, when the print head 100 is moved in an opposite direction as described above, resulting in the reset plate 134 shifting a shaft 136 of the position determining bearing 124, the engagement of the filter holder 118 is released by the position determining bearing 124 and the spring 130 allows the filter holder 118 to move toward a direction of the abutment 132.
A writing operation on the film 102 using the above-described structure will be described using FIG. 16. There is shown in FIG. 16 a moving chart of the print head 100. As shown, reference numeral xe2x80x9caxe2x80x9d indicates a filter reset position, a region between reference numerals xe2x80x9cbxe2x80x9d and xe2x80x9ccxe2x80x9d is referred to as an accelerating region, a region between reference numerals xe2x80x9ccxe2x80x9d and xe2x80x9cdxe2x80x9d is an exposure region, and a region between reference numerals xe2x80x9cdxe2x80x9d and xe2x80x9cfxe2x80x9d is a change-over region of the filters R,G,B. Further, xcex94 marks in the drawing is referred to as a position of the luminous source 110, i.e., a luminous dot row. In the above-described print head 100, a full-color image is formed on the film 102 by color-separating an image into three images of primary colors of R,G,B and superposing the three images.
As shown in FIG. 16, the reset plate 134 moves the shaft 136 of the position determining bearing 124 when the print head 100 is moved to the xe2x80x9caxe2x80x9d position, which, in turn, results in the filter holder 118 moving to right by the elastic force of the spring to be reset at an initial position. At this position, the filter R is set at a light irradiating position (referred to as xcex94 mark) of the luminous element 110.
The printer head 100, as shown in FIG. 16, accelerates at a regular speed through the accelerating region, i.e., between xe2x80x9cbxe2x80x9d and xe2x80x9ccxe2x80x9d along the sub-scanning direction and moves to the exposure region, i.e., between xe2x80x9ccxe2x80x9d and xe2x80x9cdxe2x80x9d. In synch with this operation, the luminous element 110 is driven with an image signal of red R, forming the image in red R on the film.
Furthermore, at the completion of the forming of the image in red R on the film, the projection 120 of the filter holder 118 comes in contact with the abutment 132 at the changing-over region, allowing the filter holder 118 to move and the filter to change-over from red R to green G.
Next, the print head 100 moves to the xe2x80x9cbxe2x80x9d position. At this position, since the reset plate 134 and the shaft 136 of the position determining bearing 124 are not in contact with each other, the filters are not reset. The print head, as shown in FIG. 16, is accelerated at the regular speed through the accelerating region along the subscanning direction and moves to the exposure region. In synch with this operation, the luminous element 110 is driven with an image signal of green G, forming an image in green G on the film. At the completion of the forming of the image in green on the film, the projection 120 of the filter holder 118 comes in contact with the abutment 132 at the change-over region, i.e., between xe2x80x9cexe2x80x9d and xe2x80x9cfxe2x80x9d, allowing the filter holder 118 to move and causing the filter to change-over from green G to blue B.
Again, the print head 100 moves to xe2x80x9cbxe2x80x9d position. At this position, since the reset plate 134 and the shaft 136 of the position determining bearing 124 are not in contact with each other, the filters are not reset. Further, the print head 100, as shown in FIG. 16, is accelerated at the regular speed through the accelerating region and moves to the exposure region. In synch with this operation, the eluminous element 110 is driven with an image signal of blue B, forming an image in blue B on the film.
Next, the print head 100 moves to the xe2x80x9caxe2x80x9d position as shown in FIG. 16, the reset plate 134 and the shaft 136 of the filter holder 124 come in contact with each other and the filter is reset as red R.
As described above, in the conventional optical printer, the print head 100 is movable in the sub-scanning direction with respect to the film 102 placed at a desired position. Further, the print head 100 is constructed in such a way that the change-overs among the filters R,G,B being movable in the sub-scanning direction, are accomplished only by the movement thereof.
However, in the conventional optical printer as described, the change-over from green G to blue B takes place when the print head 100 moves and comes in contact with the abutment 132 shown at the right side in FIG. 15 and the resetting to red R takes place when the print head 100 moves and comes in contact with the reset plate 134 shown at the left side in FIG. 15. In other words, there are formed on, both right and left, change-over regions, the change-over resulting from the print head 100 moving. The existence of change-over regions in two opposite direction runs counter to the down-sizing of the optical printer.
In addition, during the change-over from green G to blue B, since an independent change-over region, i.e., between xe2x80x9cdxe2x80x9d and xe2x80x9cexe2x80x9d and xe2x80x9cexe2x80x9d and xe2x80x9cfxe2x80x9d in FIG. 16 exists at each of the pitches of the filters of green G and blue B, the print head must move accordingly. Further, the description above is referred to a situation where only three filters of R,G,B are used. However, if three or more filters are required to change-over, the print head 100 must move accordingly, except for one pitch of one filter.
Further, even though the amount of movement of the print head 100 is controlled by recognizing a pulse number of the pulse motor 106, the amount of movement thereof required is different, as shown in FIG. 16, when it moves from right to left and vice versa, thereby making the control thereof difficult and complicated.
It is, therefore, an object of the present invention to provide an optical printer and a print head therefor capable of small-sizing of an apparatus by reducing a moving amount of the print head and simplifying a control according to the movement of the print head.
In accordance with one aspect of the present invention, there is provided an optical printer for optical writing on a recording medium and having a print head with a luminous source and a plurality of filters selectively set to a luminous section of the luminous source by moving toward a predetermined direction with respect to the luminous source, and a moving means for allowing the print head to be reciprocated in the predetermined direction, the optical printer comprising: a transfer means disposed the print head and for allowing the filters to be moved to the predetermined direction by a regular amount, thereby setting a desired filter to the luminous source; an abutting means disposed to one end side of the moving region of the print head and is abutted to the transfer means when the print head is moved to one end side of the moving region, thereby allowing the transfer means to operate in the regular amount; and a reset means disposed to the print head and operated at the same side as the abutting means for resetting the filter to its initial position when the print head is moved more than the moving region.
In a preferred embodiment of the present invention, the optical printer further may include an accelerating region for accelerating the print head at a regular speed to the other end side of the moving region by being disposed to the same side as the abutting portion.
In a preferred embodiment of the present invention, each of the filters may have a predetermined pitch in the predetermined direction and is maintained in a filter holder resiliently supported to be moved toward the predetermined direction with respect to the luminous source, the transfer means may include a transferring portion detachably engaged to the filter holder and for moving the filter holder by the predetermined pitch of the filters against the elastic force by the regular amount to be abutted to the abutment, and an engagement engaged with the filter holder moved by the transferring portion against the elastic force, thereby positioning a desired filter to correspond to a position set to the luminous source, and the reset means may be positioned at the same side as the abutting portion and may release simultaneously the filter holder from the engagement and the engagement of the transferring portion with the filter holder when the print head is moved more than the moving region.
In accordance with the other aspect of the present invention, there is provided a print head of an optical printer for optical writing on a recording medium during moving toward a predetermined direction by a moving means, the print head comprising: a base having a luminous source and movably disposed in the predetermined direction by the moving means; a filter holder having a predetermined pitch toward the predetermined direction to thereby maintain a plurality of filters therein and resiliently supported to the base to allow the filters to be moved toward the predetermined direction on the luminous source; a transfer means abutted to one portion of the optical printer when the base is moved to one end side of the moving region by the moving means and engaged to allow the filter to be moved by the predetermined pitch toward the predetermined direction by the regular amount against the elastic force so that a desired filter is set to the luminous source; and a reset means for releasing the engagement with the filter holder in the transfer means when the base is moved more than the moving region from one end side of the moving region.
In a preferred embodiment of the present invention, the transfer means may include a transferring portion detachably engaged to the filter holder and for moving the filter holder to be moved by the predetermined pitch of the filters against the elastic force of the filter by the regular amount to be abutted to a portion of the optical printer, and an engagement engaged with the filter holder moved by the transferring portion against the elastic force, thereby positioning the desired filter to correspond to a position set to the luminous source, and the reset means may simultaneously release the filter holder from the engagement and the engagement of the transferring portion with the filter holder when the base is moved more than the moving region from one end side of the moving region.